Recommended Lactulose Dosage per Kilogram
For hepatic encephalopathy, the recommended lactulose dosage is 20-30 g (30-45 mL) administered 3-4 times daily, titrated to achieve 2-3 soft bowel movements per day. 1, 2
Adult Dosing Guidelines
- Initial dose for hepatic encephalopathy: 30-45 mL (20-30 g) every 1-2 hours until at least 2 soft bowel movements are produced daily 1
- Maintenance dosing for hepatic encephalopathy: 20-30 g (30-45 mL) administered 3-4 times daily 1, 2
- For constipation: Initial dose of 10-20 g (15-30 mL) daily, which may be increased to a maximum of 40 g (60 mL) daily if needed 1
- Dose should be adjusted based on clinical response with the goal of achieving 2-3 soft bowel movements per day 1, 2
Pediatric Dosing Guidelines
- For prevention of essential fatty acid deficiency in preterm infants: A minimum linoleic acid intake of 0.25 g/kg/day is recommended 3
- For prevention of essential fatty acid deficiency in term infants and children: A minimum linoleic acid intake of 0.1 g/kg/day is recommended 3
- For constipation in children: 250-400 mg/kg/day of lactitol or 500-750 mg/kg/day of lactulose 4
Administration Routes
- Oral administration is preferred when possible 3, 1
- For patients with severe hepatic encephalopathy (West-Haven criteria grade 3 or more) who cannot take medications orally: Enema of 300 mL lactulose and 700 mL water can be performed 3-4 times per day 3
- When administering as an enema, the solution should be retained in the intestine for at least 30 minutes 3
Dosing Considerations and Pitfalls
- Excessive use can lead to complications including dehydration, hypernatremia, and severe perianal skin irritation 1, 2
- Overuse may paradoxically precipitate encephalopathy in patients with liver disease 1, 5
- Bloating and flatulence are common dose-dependent side effects that may limit use 1, 2
- If excessive bowel movements occur (more than 2-3 per day), the dose should be reduced to prevent complications 2
Alternative Treatments
- Rifaximin (400 mg three times/day or 550 mg twice/day) can be considered as an alternative or adjunct to lactulose 3, 2, 5
- Lactitol can be used as an alternative to lactulose at an equivalent daily dose of 67-100 g 3, 2
- For patients who develop significant diarrhea on lactulose, temporarily holding lactulose and starting rifaximin is recommended 5
Efficacy Evidence
- Lactulose has been shown to be effective in treating constipation with significant improvement in stool consistency and frequency compared to placebo 6
- In postpartum constipation, lactulose at 15 mL once daily with maintenance dose of 5-15 mL has demonstrated effectiveness 7
- Lactulose produces an osmotic laxative effect that helps eliminate ammonia in hepatic encephalopathy 2